On 5/26/2016 10:19 AM, Peter Zijlstra wrote:
--- a/arch/tile/lib/spinlock_32.c
+++ b/arch/tile/lib/spinlock_32.c
@@ -72,10 +72,14 @@ void arch_spin_unlock_wait(arch_spinlock
if (next == curr)
return;
+ smp_rmb();
+
/* Wait until the current locker has released the lock. */
do {
delay_backoff(iterations++);
} while (READ_ONCE(lock->current_ticket) == curr);
+
+ smp_acquire__after_ctrl_dep();
}
EXPORT_SYMBOL(arch_spin_unlock_wait);
--- a/arch/tile/lib/spinlock_64.c
+++ b/arch/tile/lib/spinlock_64.c
@@ -72,10 +72,14 @@ void arch_spin_unlock_wait(arch_spinlock
if (arch_spin_next(val) == curr)
return;
+ smp_rmb();
+
/* Wait until the current locker has released the lock. */
do {
delay_backoff(iterations++);
} while (arch_spin_current(READ_ONCE(lock->lock)) == curr);
+
+ smp_acquire__after_ctrl_dep();
}
EXPORT_SYMBOL(arch_spin_unlock_wait);
The smp_rmb() are unnecessary for tile. We READ_ONCE next/curr from the
lock and compare them, so we know the load(s) are complete. There's no
microarchitectural speculation going on so that's that. Then we READ_ONCE
the next load on the lock from within the wait loop, so our load/load
ordering is guaranteed.
With that change,
Acked-by: Chris Metcalf <cmetcalf@xxxxxxxxxxxx> [for tile]
--
Chris Metcalf, Mellanox Technologies
http://www.mellanox.com
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